Tagged: lubricants

Lubricant Degradation / Oil Properties / Reliability / Storage & Handling of Lubricants / Used Oil Analysis

Role of Condition Monitoring, Human & Organizational Factors in Oil Failures

Choosing the right oil for the system is just one part of the puzzle. How do we know the oil is performing when it’s in the system? This is where condition monitoring can work hand in hand to help ensure that the oil does not fail the asset.

If a proper oil analysis program does not exist, operators will not know whether the oil is properly lubricating the asset. They will also not be aware of whether the oil is breaking down too quickly and failing to protect the asset. Oil analysis can also alert operators to signs of wear in the asset, so they can fix them before they turn into functional failures.

An oil analysis program that lives in a drawer protects assets about as well as no program at all.

There is also the possibility that an oil analysis program exists but is not top of mind, or that its results are put in a drawer. This can also cause the asset to fail even though the correct oil is being used. Apart from the aforementioned factors, if operators are not warned of the impending failure of the oil, this can result in production losses, increased downtime, and, in some extreme cases, the complete loss of the asset if it has failed beyond repair.

Incorrect sampling is another area in which the actual condition of the asset is not reported. Even with the correct oil used, if a sample is collected from a dead leg or an area that is not truly representative of the conditions inside the component, its actual condition will not be known. With incorrect data about the component, the asset can be misdiagnosed or treated for symptoms that do not exist, which can lead to its detriment.

Human and Organizational Factors

Not all failures occur at the equipment level; human and organizational factors can also cause the asset to fail even when the correct oil is used. If humans aren’t properly trained in oil sampling techniques or storage and handling practices, these can affect the asset’s functionality. We often forget that, at the heart of it all, lies the human factor, which is partially governed by the organization’s systems.

Training needs are an organizational factor that is often overlooked when considering how an asset can fail. However, if operators have not been trained in condition monitoring techniques, they will not be able to read oil analysis reports or take appropriate actions to protect the asset. Training can help bridge some competency gaps that directly impact asset performance.

It doesn’t matter what oil is in the system if no one is trained to monitor it – or motivated to care.

Culture is another factor swept under the rug. If the culture doesn’t exist to look after the assets, it doesn’t matter what type of oil is placed in the system; the asset will fail eventually. The performance of the asset does not only rely on using the correct oil. By implementing a culture of Asset ownership, where operators look after the asset and are accountable for its performance, assets are optimized to provide the functionality they should. This is one way to ensure the right oil is used to enable the assets’ performance.

Another area of concern is the documentation of maintenance procedures. If maintenance procedures are not adequately documented, someone new to the operation may not be aware of the correct practice. This, coupled with a lack of training, can spell disaster for the equipment. In these cases, even though the right oil was selected, the wrong practice or lack thereof can fail the asset.

Turning the “Right oil” into the “Right Outcome.”

As explained in this article, improper practices can jeopardize the asset’s health, even when the right oil is used. However, if all the right things align, we can have an asset that lasts for its expected lifetime or beyond.

This starts with selecting the right oil based on the application, environmental conditions, and OEM recommendations. If we follow this up with good storage and handling practices, proper condition-monitoring programs, documentation, and training, we can look toward a longer-lasting asset. The right oil enables reliability – but only disciplined practices deliver it.

Find out more in the full article, "When 'Right oil, Wrong practice' still fails assets" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
February 22, 2026
Lubricant Degradation / Oil Properties / Reliability / Storage & Handling of Lubricants / Used Oil Analysis

Common Modes of Failure for Lubricants

Regardless of the oil selected, common modes of failure can occur with every lubricant. These include: contamination, improper storage and handling practices, and environmental factors as shown in Figure 4.

Figure 4: Common modes of failure for lubricants
Figure 4: Common modes of failure for lubricants

Contamination can be defined as any foreign particle entering the system. This includes any gases, liquids, or solids. Especially when the lubricant system runs alongside the process side, process gases and liquids can leak into the oil. These contaminants can influence the oil’s degradation, leading to deposits or chemical reactions that break it down. Common process contaminants include ammonia or treated water.

The biggest threat to the right oil is often what gets added to it – whether it’s process contamination or the wrong oil during a top-up.

Another liquid that can contaminate oil is another oil. During top-ups, operators can add the wrong oil to the system, causing contamination and, depending on the oil, a possible shutdown. Adding motor oil to hydraulic oil can be catastrophic, as the additive packages work differently and the motor oil additives may counteract the hydraulic additives, removing them from the oil, leaving the asset open to wear and failure. Despite selecting the correct lubricant for your system, adding the wrong oil (mistakenly) will shorten its lifecycle and cause the asset to fail.

Bad storage and handling practices can also erode your oil, regardless of the oil you choose. Turbine and hydraulic oils are used in precise equipment. As such, they need to be clean and free of dirt or other contaminants. However, if oils are not stored correctly, contaminants can enter and contaminate the oil.

Simple techniques, such as transferring oil from larger storage containers (pails, drums, or totes) into smaller, more manageable containers (2-3 liters or less), can introduce contaminants into the oil if not done correctly. If oils are to be transferred to another storage container, the storage container must be clean. The transfer process should use clean hoses (not previously used for another lubricant) and be completed in a dust-free environment.

If you wouldn’t use a dirty needle for a blood transfusion, why would you use a dirty hose for an oil transfer?

The transfer of oils from one container to the next can be thought of as a blood transfusion. Would you use dirty needles or vials to transport the blood to be placed into another human? Similarly, oil can be likened to the equipment’s lifeblood and should be treated accordingly. Just as we observe sterile practices for blood transfusions, we should also observe similar types of practices for oil transfers.

Environmental and operational factors can also influence lubricant degradation. As stated earlier, all lubricants can degrade over time under harsh conditions. The lubricant formulation largely influences this, as does whether it was blended to withstand those conditions.

Oxidation can easily occur when temperatures increase, free radicals are present, or when wear metals are present. Thermal degradation occurs when the temperatures exceed 200°C. On the other hand, microdieseling occurs in the presence of entrained air, despite the lubricant used in the system, as shown in Figure 5.

Figure 5: Lubricant Degradation Processes
Figure 5: Lubricant Degradation Processes

Any of these degradation mechanisms can occur regardless of the type of oil chosen. Hence, it is essential to remember that operational conditions and environmental factors can heavily influence oil degradation, even when the oil is appropriate for the system.

Find out more in the full article, "When 'Right oil, Wrong practice' still fails assets" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
February 22, 2026
Oil Properties / Reliability

Spec Sheet vs Strategy for choosing the right oil

Sometimes we can spend hours poring over technical data sheets, comparing oil performances, and finally selecting the “right” oil which aligns with the needs of our equipment. Then, within 2 months, the oil degrades, our machines shut down, and we have a bunch of maintenance repairs lined up. What went wrong? We clearly had the “right” oil in the equipment; everything should have worked beautifully. This is where the awareness of lubrication and its practices becomes critical.

Having the correct oil is only one part of the puzzle. Being able to deliver that oil in its purest, cleanest form to the machine is often one of the other pieces that go missing. Another piece is selecting the right oil, not just based on the sales guy’s advice, but on the actual operating conditions of your machine. In this article, we dive a bit deeper into ways you can align the right oil with the proper practices, or avoid the wrong ones, to help extend the life of your asset.

Spec Sheet vs Strategy

For this example, we will consider a turbine oil selection. If a customer wants to change the oil in their turbine, then they may consider the following:

  • What are the OEM specifications that need to be met?
  • Is this oil available from the local supplier?
  • How does it compare to other oils on the market?
  • Does the cost justify the value? (or will the purchasing department want something cheaper?

For most of these questions, engineers or the person tasked with selecting the oil can readily find the answers in the oil’s technical data sheet and by talking to their sales representative. But if we dive a bit deeper, are we selecting the right oil for the operating and environmental conditions? Let’s examine the selection of a turbine oil for the Siemens SGT 200 Gas turbine that meets the Siemens TLV 9013 04 specification.

As seen in this document from Shell Lubricants, a few of their products meet that specification, namely Shell Turbo T, Turbo S2GX, Turbo S4X & Turbo S4GX.

Figure 1: Shell Turbo Family for the Siemens TLV 9013 04 Specification
Figure 1: Shell Turbo Family for the Siemens TLV 9013 04 Specification

On the other hand, Mobil provides some solutions as well, namely, Mobil DTE 732, 746, or DTE 832, 846

Figure 2: Mobil DTE 700 & 800 Series meeting the Siemens TLV 9013 04 Specification
Figure 2: Mobil DTE 700 & 800 Series meeting the Siemens TLV 9013 04 Specification

Chevron also provides an option of Chevron GST as follows:

Figure 3: Chevron GST oil meeting the Siemens TLV 9013 04 specification
Figure 3: Chevron GST oil meeting the Siemens TLV 9013 04 specification

With so many options, how can one choose the “right” oil? They all meet the required Siemens specification, TLV 9013 04. This is where the data sheets, OEM manual, and knowledge of the equipment’s operating conditions play a crucial role.

As per the manual, there are preset conditions for temperatures and pressures, but if your actual system runs hotter (or production is being pushed a bit more), it is functioning outside the operating envelope.

The spec sheet tells you what the oil can do. Your operating conditions tell you what it must do.

Additionally, if your surroundings are harsh (close to the sea or in a corrosive environment, or in a non-ventilated area where heat can build up), these can place additional stress on the equipment. For these harsher conditions, a synthetic oil might be more appropriate than a mineral oil, albeit more expensive in terms of the initial investment.

The manual also specifies which tests/characteristics should be used to monitor the condition of the oil, namely: viscosity, particle count, water content, demulsibility, air release, foaming characteristics, RULER®, and MPC. Based on the performance of your current oil in the system, you can determine whether these values fluctuate toward the higher warning zones. This can also influence your decision about which oil to choose.

It’s not just about the right oil or one that aligns with OEM requirements. The selection should also be based on the environmental conditions of the oil and the equipment, and on whether the oil is suited to perform in these conditions. A mineral oil will not withstand the temperatures that a synthetic oil can for extended periods without degrading. Similarly, given the “right” conditions, synthetic oils can also degrade. By cross-examining your spec sheet, OEM manual, and actual conditions, you can determine the best-suited oil for your operations.

Find out more in the full article, "When 'Right oil, Wrong practice' still fails assets" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
February 22, 2026
Oil Properties / Used Oil Analysis

Critical Condition Monitoring Tests for Compressor Oils

To ensure these oils remain healthy (and not contaminated or degraded), a few basic tests can be performed on all compressors, regardless of type (reciprocating, screw, refrigerant, etc.). These include:

  • Viscosity – this is key as some of the gases can easily affect the viscosity, which (if decreased) will not provide adequate separation for the interacting surfaces and cause wear. Generally, a ±10% limit is used (though OEMs may use different values).
  • Acid Number – if this begins increasing, then we have an accumulation of acids in the oil, which can be because of contamination. For most compressors, a 0.2 mg KOH/g increase is the warning limit, but for refrigeration compressors, the limit is tighter at +0.1 mg KOH/g. Always check with your OEM for these limits.
  • Water content – changes by OEM and refrigerant type, as the different gases will have varied tolerances.
  • Wear metals – these values will vary as per OEM, as well, since they are all designed with different types of metals. Users should look for trends or significant increases in these values to indicate wear.

Some specialty tests for compressors include:

  • MPC (Membrane Patch Colorimetry) – this helps to measure if there is any potential for the oil to form varnish. Given the high temperatures these types of equipment endure and the potential for contamination, the oil is at risk of forming varnish. While limits will vary by OEM, some general guidelines to follow are 0-20 Normal, 20-30 Warning, >30 Action required
  • RULER® (Remaining Useful Life Evaluation Routine) – this quantifies the remaining level of antioxidants in the oil. When oxidation occurs, the antioxidants get depleted. As such, by monitoring antioxidant levels, one can easily determine whether oxidation is happening in the oil. The general rule of thumb is that if the level falls below 25%, there are not enough antioxidants to keep the oil healthy and prevent degradation.
  • Air Release (DIN ISO 9120) – measures the ability of the oil to allow air to escape and not keep the air in the oil. If air bubbles remain in the oil, this can be devastating, as it can lead to micropitting, cavitation, or increased oxidation. Users can trend the values; if they increase, it indicates that the air is taking longer to be released, which means it is staying in the oil and in the system longer.
  • Particle Count – this can identify if there are any contaminants in the system. These oils must be kept clean, and OEMs typically specify target cleanliness levels.

Compressors are critical equipment, and we must understand how they work and the lubricant specifications required. Monitoring their health can also help us avoid unnecessary downtime and keep our facilities running.

References

  1. Mang, T., & Dresel, W. (2007). Lubricants and Lubrication. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA.
  2. Totten, G. E. (2006). Handbook of Lubrication and Tribology – Volume 1 Application and Maintenance – Second Edition. Boca Raton: CRC Press.
  3. Shell Lubricants. (2025, November 08). The Shell Corena range. Retrieved from Shell Lubricants Compressor Oils: https://www.shell.com/business-customers/lubricants-for-business/products/shell-corena-compressor-oils/_jcr_content/root/main/containersection-0/simple_1354779491/promo_1484925192/links/item0.stream/1759302155345/17be2a9a74057f321bb209128933f68f8b88ca70/s
  4. ExxonMobil. (2025, November 08). Refrigeration Lubricant Selection for Industrial Systems. Retrieved from ExxonMobil Lubricants: https://www.mobil.com/lubricants/-/media/project/wep/mobil/mobil-row-us-1/new-pdf/refrigeration-lubricant-selection-for-industrial-systems.pdf
  5. Chevron Lubricants. (2025, November 08). Optimizing compressor performance and equipment life through best lubrication practices Chevron. Retrieved from Chevron Lubricants: https://www.chevronlubricants.com/content/dam/external/industrial/en_us/sales-material/all-other/Whitepaper_CompressorOils.pdf

Find out more in the full article, "Compressor Oil, Types, Applications and Performance Drivers" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
January 7, 2026
Oil Properties

Refrigeration Lubricants

For industrial refrigeration systems, there are a couple of essential pieces of information to consider before selecting the most suitable oil. The user must know the refrigerant in use, the evaporator type (dry or wet; carryover < 15%), the evaporator temperature, the compressor type, and the outlet temperature.

The refrigerant fluids are classified as per the ASHRAE classification (ANSI-ASHRAE Standard 34-2001):

  • R717 — Ammonia
  • R12 — Chlorofluorocarbon (CFC)
  • R22 — Hydrochlorofluorocarbon (HCFC)
  • R600a — Isobutane
  • R744 — Carbon dioxide (CO2)
  • R134a, R404a, R507 — Hydrofluorocarbons (HFC)

It should be noted that CFCs were banned under the Montreal Protocol (1989) due to their Ozone Depletion Potential, and HCFCs are being phased out due to their Global Warming Potential.

Chevron provides some general guidelines for selecting the appropriate refrigerant, as shown in the table below.5

(But you should always follow the guidelines of your OEM when selecting the appropriate lubricant.)

Table 1: Refrigerants and their associated lubricant technologies

ExxonMobil classifies its refrigeration lubricants based on refrigerant type, evaporator temperature, and compressor type (Piston, Screw, or Centrifugal). This is very helpful when determining the best-suited lubricant for your refrigerant compressor.

Check out the pdf here.

 

Find out more in the full article, "Compressor Oil, Types, Applications and Performance Drivers" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
January 7, 2026
Oil Properties

Industry Standards for Compressor Oils

Some other classifications which users may see when dealing with compressor oils (even though some of these standards may be dated) include:

ISO 6743-3, which uses the following acronyms for associated compressors:

  • DAA, DAB, DAG to DAJ: Air compressors
  • DVA to DVF: Vacuum pumps
  • DGA to DGE: Gas compressors
  • DRA to DRG: Refrigeration compressors

 

In this standard, the “D” family includes detailed classifications of lubricants used in air, gas, and refrigeration compressors. The second letter usually indicates the type of compressor, and the third letter indicates the application severity or type, especially for gas or refrigeration compressors.

For instance;

DAJ represents:

D -> Compressor Lubricant

A -> Air compressor

J-> Lubricant drain cycles of >4000 hours

DVB represents:

D-> Compressor Lubricant

V->Vacuum pumps, Positive Displacement Vacuum pumps with oil lubricated compression chambers, Reciprocating and rotary drip feed, Rotary oil-flooded (vane and screw)

B-> Low vacuum for aggressive gas (102 to10-1kPa or 103 to 1 mbar)

DGD represents:

D-> Compressor Lubricant

G-> Positive displacement reciprocating and rotary compressors for all gases, Compressors for refrigeration circuits or heat pump circuits, together with air compressors, are excluded.

D-> Gases that react chemically with mineral oil, usually synthetic fluids, HCI, CI2, O2, and oxygen-enriched air at all pressures. CO2 at pressures above 103 kPa (10 bar) with O2- and oxygen-enriched air: mineral oils are prohibited, and very few synthetic fluids are compatible.

DRB represents:

D-> Compressor Lubricant

R-> Compressors, refrigeration systems

B-> Ammonia (NH3), Miscible, Polyalkylene glycol, Commercial and industrial refrigeration, For direct expansion evaporators; PAGs for open compressors and factory-built units.

Another standard which is also used in this industry is DIN 51506, which defines:

  • VB, VC: Uninhibited mineral oils (no oxidation inhibitors)
  • VBL: Mineral oil-based engine oil (additives that protect from corrosion and oxidation and air compressor temperatures up to 140°C)
  • VCL: Mineral oil-based engine oil (additives that protect from corrosion and oxidation and air compressor temperatures up to 160°C)
  • VDL: Inhibited oils with increased aging resistance (additives that protect from corrosion and oxidation and air compressor temperatures up to 220°C, recommended for compressors with 2-stage compression)

One more standard is DIN 52503, which has these classifications:

  • KAA: Not miscible with ammonia
  • KAB: Miscible with ammonia
  • KB: For carbon dioxide (CO2)
  • KC: For partly and fully halogenated fluorinated and chlorinated hydrocarbons (CFC, HCFC)
  • KD: For partly and fully fluorinated hydrocarbons (HFC, FC)
  • KE: For hydrocarbons (e.g., propane, isobutane)

These standards are referenced when discussing certain compressor oils, and their definitions are helpful for navigating acronyms.

Find out more in the full article, "Compressor Oil, Types, Applications and Performance Drivers" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
January 7, 2026
Oil Properties

Types of Compressors and Oils

Compressors are integral to many of our operations. They are used to compress gas, increasing its pressure, and to power tools. They can also be used as vacuum pumps or blowers, but each application is different. As such, they require various types of lubrication, particularly for applications that use specific refrigerants and come into contact with the lubricant.

In all these applications, the functions of the oil remain largely the same: it must lubricate the surfaces, prevent wear and corrosion, maintain the required viscosity, and provide proper sealing.

In this article, we will dive into the various types of compressor oils and explain why they are suited to these applications. We will also discuss monitoring the health of these oils and the tests that should be performed to ensure your compressor oils remain healthy.

Types of Compressors

Essentially, there are two main types of compressors: Displacement and Dynamic. For displacement compressors, gas is drawn into a chamber, compressed, and expelled by a reciprocating piston. On the other hand, for dynamic compressors, turbine wheels accelerate a medium, which is then abruptly accelerated.1

Positive displacement compressors include Reciprocating and Rotating compressors. These can be further subdivided as shown in Figure 1. For Dynamic (Turbo) compressors, these are further subdivided into Centrifugal, Axial, and Mixed types (also shown in Figure 1).

Figure 1: Types of compressors
Figure 1: Types of compressors

Depending on the type of compressor, the required lubricant will vary. For example, positive-displacement compressors use rolling or sliding motion and include bearing and sealing components within the compression chamber. On the other hand, dynamic compressors use hydrodynamic journal and thrust bearings, or rolling-element bearings, to support the main shaft, which is isolated from the compression chamber.

Working pressures, temperatures, and the type of gas being compressed also play a significant role in determining the appropriate lubricant.2

As with most applications, there can be a dry-sump or a wet-sump. Wet sumps are typically seen in reciprocating and rotary screw compressors.  In a wet sump, the gas usually contacts the oil, lowering its viscosity. This is where it is essential to note the gas’s solubility in the system oil. Natural gas and other hydrocarbons are more soluble in mineral oils and PAOs than in PAGs and diesters. Thus, PAGs may be preferred in some cases to avoid lubricant failure.

Compressor Oils

Most of the major global lubricant OEMs have classified their oils based on:

  • Rotary vane and screw air compressor oils
  • Reciprocating (piston) air compressor oils
  • Refrigeration compressor oils

As seen below in Figure 2, Shell Lubricants3 has a line of lubricants, particularly for air compressors, which are further classified into mineral oils, PAOs, and PAGs for Rotary vane and screw air compressors or Reciprocating (piston) air compressors.

Figure 2: Shell Lubricants for Air Compressors
Figure 2: Shell Lubricants for Air Compressors

In reciprocating air compressors, cylinder design dictates the lubrication type, as this is the most severe application. Compressing the gas usually results in high temperatures, which can easily lead to oxidation. The compressed gas must be free of contaminants, as contaminants can accelerate oxidation. Typically, for reciprocating air compressors, mineral oils or PAO- or di-ester-based lubricants in the ISO VG 68 to 150 range are preferred.

Rotary vane compressors can experience pressure extremes as the vanes slide to compress the gas, and oil is continuously injected into the compressor chambers. Typically, ISO VG 68-150 oils are used in this application.

Figure 3: Reciprocating Piston vs Screw Compressor Lubricant Needs
Figure 3: Reciprocating Piston vs Screw Compressor Lubricant Needs

For screw compressors, the oil must perform several functions, including lubricating the meshing rotors and the plain and roller bearings that form part of the geared coupling. ISO VG 46 mineral oils are usually used in these compressors, but the viscosity can be increased to ISO VG 68 or to synthetic PAO or PAG lubricants at higher ambient temperatures. Similarly, Group III base oils of these viscosities can be used in this area. Most screw compressor oils contain mild EP/AW performance additives and require an FZG failure load≥10.

Ideally, reciprocating piston compressors will use higher viscosities (ISO VG 100-150) with extremely low carbon residue and no or mild EP/AW additives. Conversely, screw compressors will use lower viscosities (ISO VG 46 or 68) with excellent oxidation stability and mild/high AW/EP additives1, as shown in Figure 3.

Find out more in the full article, "Compressor Oil, Types, Applications and Performance Drivers" featured in Precision Lubrication Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
January 7, 2026
Oil Properties / Used Oil Analysis

Interpreting the Oil Analysis Report in Practice

Now, we will actually read a report to help put all of these into practice.

Here is a sample report from Eurofins for a turbine oil. In this report, the various types of tests are classified according to wear metals, additives, and contaminants, as shown in Figure 2.

According to the report, samples have been collected over a period of time. This helps with the trending of the data, so we can spot when the values start varying from the “normal levels”. The reference values are also provided in the first column to help users determine whether these values fall within tolerance limits or not.

Figure 2: Sample Turbine Oil Analysis Report

Typically, the lab will provide some type of traffic light system where:

  • Red – indicates there may be an abnormal reading or the oil should be changed immediately, as certain values have surpassed the critical limits.
  • Amber – shows that the values are approaching the warning limits, but there is still some time to investigate and fix the problem.
  • Green – tells us that all values are within the tolerance limits and the oil is performing normally.

For this report, they also include additional tests as shown in Figure 3.

Figure 3: Additional Tests for Turbine Oils
Figure 3: Additional Tests for Turbine Oils

For turbine oils, understanding the demulsibility of the oil is important, as this is the oil’s ability to separate from water, or rather, not to form an emulsion. Excessive water in the oil can lead to rust or even a washout of the additives.

The Foam test is also administered to detect the oil’s ability to release air from the oil, ensuring that the air doesn’t get trapped. If air is trapped, it can lead to microdieseling and cavitation on the inside of the equipment.

RPVOT – Rotating Pressure Vessel Oxidation test is also performed, as it indicates the expected oxidation of the oil. MPC (Membrane Patch Colorimetry) and Ultracentrifuge detect the potential of the oil to form varnish, and the RULER® values give the actual quantity of antioxidants present.  These values are all critical for monitoring the health of the turbine oil, as it is very susceptible to oxidation and the formation of varnish.

In essence, reading the oil analysis report involves understanding what the tests are meant to measure, knowing your equipment and its operating conditions, and having a history of your equipment.  These factors all contribute to trending the data to ensure that there are no surprises with unplanned downtime due to wear or oil degradation.

References

Eurofins. (2025, September 06). Annual Turbine Analysis. Retrieved from Eurofins Testoil: https://testoil.com/services/turbine-oil-analysis/annual-turbine-analysis/

Find out more in the full article, "How to Read Oil Analysis Reports and translate Data into Reliability" featured in Reliable Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

by
November 15, 2025
Oil Properties / Used Oil Analysis

How to Interpret Your Oil Analysis Results

Have you ever received your bloodwork results from your doctor, only to be more confused than ever? With all the long names and numbers just sitting on the piece of paper, Google (or ChatGPT) becomes your best friend to help interpret what they mean. However, even with these tools of reason, there is usually a disclaimer that states, “Please consult your doctor for a more accurate interpretation”.

Numbers alone don’t tell the whole story – context is what makes oil analysis meaningful.

One of the reasons for constantly looping your doctor back into the mix is that they have your history, they know how your body responds to certain things, and values which may get flagged because they are outside of the limits may be waived away by your doctor because it is normal for your body based on your history and DNA.

The same applies to oil analysis. Depending on the application and operating environment, certain conditions may be met that can be interpreted as unusual. Still, if you’re familiar with your system, you will understand the reason behind the numbers.

Figure 1: DIN 515519 table showing viscosity limits
Figure 1: DIN 515519 table showing viscosity limits

Viscosity

As mentioned earlier, viscosity is the most important characteristic of a lubricant. If it is too thick for the application, this can lead to efficiency loss, increased heating, and a slowdown of the system. Essentially, a significant amount of work needs to be done on the oil to make it compatible with the application.

On the other hand, if it is too thin, then we run the risk of improper lubrication. Therefore, we increase the chances of wear occurring in the applications.

Viscosity is usually measured at either 40°C (for industrial applications) or 100°C (for engine applications). However, most labs put a ±5% tolerance limit for many oils. But why use such a random figure? The DIN 51519 table is used to determine ISO viscosity, with each value within a 10% range, as shown in Figure 1.

When you see an ISO VG 100 oil, the chances are that the actual viscosity of that oil varies between 90-110cSt. Therefore, if we start seeing our results vary by around 5% or trend towards the outer limits of any viscosity class, we know that something is going on with our oil.

Presence of Wear Metals

Wear metals prove that some type of wear is occurring. However, depending on their quantity, they can also provide some more insights into what is actually wearing away and whether it is normal wear or abnormal wear. Wear is reported in parts per million (ppm) or as a percentage. Here’s how to convert those percentages to ppm:

100% = 1,000,000ppm

1% = 10,000ppm

0.1% = 1,000ppm

The most common wear metals tested include Aluminum, Iron, Chromium, Copper, Lead, and Tin. Depending on the application, there are varying levels at which these will be flagged.

Table 1 provides an example of various applications and their respective limitations. These will vary based on your OEM and environment, but can be used as a general guideline. All numbers in Table 1 are in ppm.

Table 1: Wear metal limits for various applications
Table 1: Wear metal limits for various applications

AN/BN and the Presence of Contaminants

Contaminants are any foreign material in the system. Sometimes, lab tests may not be able to detect contaminants in a system because they are not specifically designed to identify that particular contaminant.

In these cases, users would need to specify what additional contaminants the lab should look for, or perform a broader FTIR (Fourier Transform Infrared) analysis to identify all the components in the oil and then determine which of them are contaminants.

The most common contaminants tested include Silicon, Water, and Fuel. Although AN/BN (Acid Number and Base Number) may not be considered a contaminant, it helps quantify the acid in your system, which shouldn’t be there; therefore, in some ways, it can be viewed as a contaminant. However, it is primarily a physical property and is listed separately.

Acid and base numbers act like an early warning system for oil health.

Table 2: Tolerance limits for some contaminants
Table 2: Tolerance limits for some contaminants

For diesel engines, BN is measured as having high base numbers, which will decline over time as acids accumulate. If the BN value declines to around 50% of its original value, then we have an issue with the acids increasing too quickly in the oils. On the other hand, AN is used for all other industrial oils (gears, hydraulics, etc.). There are varying limits for AN depending on the application, as shown in Table 2.

Silicon usually indicates the presence of sand, which is highly abrasive. This can accelerate wear in any equipment by essentially turning the oil into sandpaper and wearing away the insides of the equipment. Some of its limits are shown in Table 2.

Water in any form is highly destructive to all assets. However, some systems can tolerate a bit more water than others. This can be due to the nature of the oils (good demulsibility) or the nature of the systems, where heat is involved to help remove the water. Water in the system can lead to an increase in viscosity and disrupt the oil layer.

As such, the lubricant will not be able to form a full film to protect the asset. Water can also create an emulsion in the oil or lead to corrosivity issues. Table 2 gives some examples of limits for various systems.

Fuel contamination is an issue for most diesel engines. The presence of fuel in your oil can lead to a lower viscosity (hence the oil can no longer protect the components) and an increase in the flash/fire point of the oil, which can be particularly dangerous. We have some limits noted in Table 2.

 

Presence of Additives

It is more challenging to place these tests in a one-size-fits-all table, as oil formulations are consistently changing. The best way to interpret these additives would be to compare them against the initial values for the finished lubricant.

For your oil analysis program, always have a representative sample of the new oil so that comparisons can be made against it as the oil ages in the system. Additionally, the presence of additives in your report when they shouldn’t be there is also a sign of contamination, likely with another type of oil.

Find out more in the full article, "How to Read Oil Analysis Reports and translate Data into Reliability" featured in Reliable Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

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November 15, 2025
Oil Properties / Used Oil Analysis

Why Different Oils Require Different Tests

Oil analysis reports often wear an invisible cloak, and only if we have a wizard capable of revealing what the numbers mean, they will more than likely end up in a drawer or file on the computer. There are many similarities between oil analysis and blood tests, as they both serve similar functions.

They both test fluids, quantify the results according to different categories, and provide envelope limits within which these values should exist. If the values fall outside these limits (either below or above), we need to take action to prevent failure of the critical asset (or human organ accordingly).

An oil analysis report is less about numbers and more about the story they reveal.

In this article, we will focus on understanding the basics of reading an oil analysis report, interpreting the results, and developing action items based on the information collected. We will take a closer look at reports on turbines (rotating equipment), gear, hydraulics, and engine oils, and what this all really means for your equipment.

Why Different Oils Require Different Tests

Before we dive into the report, we need to establish that not all oils are the same! As such, different oils are required for various types of applications. Therefore, each type of oil will require slightly different tests to determine whether it is performing optimally or not. However, there are a few tests that remain the same for all oils.

The most critical characteristic of an oil is its viscosity. As such, all oils are typically tested to determine whether their viscosity meets the requirements. Another function of the oil is to prevent wear. Thus, most oils are tested for the presence of wear particles, as this can help the user identify if any wear is occurring in the asset.

Oils should be kept clean; therefore, tests are performed to determine the presence of any contaminants, and these are carried out on most oils. Similarly, additives help oils perform their functions; hence, their presence or absence should be quantified to determine if they are indeed achieving their functions for all oils.

Tests for viscosity, the presence of wear metals, contaminants, and additives are the standard sets of tests that should be performed on any oil. There are more detailed tests that examine the specifics of various types of applications, but we will delve into these later in the article.

Find out more in the full article, "How to Read Oil Analysis Reports and translate Data into Reliability" featured in Reliable Magazine by Sanya Mathura, CEO & Founder of Strategic Reliability Solutions Ltd. 

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November 15, 2025